Ice Worms and Their Habitats on North Cascade
GlaciersNorth Cascade Glacier Climate ProjectAt right: Ice Worms in
the evening on Sholes Glacier 2010: From 2001-2001 the NCGCP has
focused on detailed field studies of ice worms. Ice worms have been
observed and collected on 20 different glaciers. From 2003-2011 NCGCP is continuing our
examination of ice worm populations in the field. The Ice Worm population
did seem to struggle with decreased in snowcover on glaciers from 2003-2005,
bare ice possibly not being as conducive an environment. Better
snowcover in 2007 and 2008 led to greater populations at least at the surface in
our surveys. In 2011 with Marieve Desjardins (Queens University, Kingston,
ON) we collected ice worms for a study of the anti-freeze proteins in ice worms.
Could these proteins exhibit the right characteristics to be of use in
transplant surgeries where keeping an organ cold, without freezing is key. Below is a You Tube
video introducing ice worms. Make no mistake their habitat has been
shrinking with glacier retreat. This is also a
global response to climate change
documented glacier by glacier and overall.
At right is an image of the start of our sampling period at 7:00 pm August, 8,
2010. There were 3 ice worms per square meter. Below that is the same
location at 8:30 pm with 800 ice worms per square meter.

Ice Worm on
Easton Glacier (Marieve Desjardins)

Ice Worms in motion on Sholes Glacier

Ice Worms Yes, worms
really do live in glaciers -- in fact, this kind (ice worms) can't live off of them!!
Their scientific name is Mesenchytraeus solifugus (Emery, 1898).
They are about 1 cm (1/4") long, and about 1 mm (1/32") wide.
Glacier ice worms are dark brown to black (although they look red or
reddish-brown when they are in water. When you see them on the glacier,
they appear as loose pieces of string in the snow or ice (see photographs
above). These ice worms are in the class
of Oligochates and family of Enchytraeidae, just like earthworms, so are
members of Annelida, or segmented worms. There are other worms called 'ice
worms' that live in ice on the ocean floor, or deep underground, but they are
unrelated to glacier ice worms. It is hard to walk in the evening
onto the snowpack of a North Cascade glaciers without squashing an ice worm.
Google earth Distribution map
file.

Just how many ice worms are there on these
glaciers? On Suiattle Glacier, (photo at left and above) on the south side of Glacier Peak, the
recorded mean density was ~2600 ice worms per square meter in 2002.
With an area of 2.7 square kilometers, this represents somewhat over 7
BILLION ice worms on this glacier! This is more than the earth's
entire human population
on just one glacier. Good thing they do not use
many natural resources each. Even higher densities have been observed on Sholes, Ptarmigan and Ice Worm Glacier.
The total population of ice worms must be decreasing as North Cascade glaciers
continue to retreat rapidly and even disappear in some cases.
Glacier retreat.Ice Worm Charts

Their Distribution:

Glacier ice worms inhabit glaciers from southern Alaska's
coastal ranges through the Coast Ranges of British Columbia, the
Cascades of Washington to the Three Sisters of Oregon and the Olympic Mountains. The
Three Sisters and Mount Hood areas is south of the Cordilleran Ice Sheet limit, indicating that this
ice sheet cannot be the only dispersal method for ice worms. It is also noteworthy that
ice worms are not found in the interior ranges of British Columbia or in the
Rocky Mountains, which is the interior side of the Cordilleran Ice Sheet.
The ice worms seem to be associated only with temperate climates.
Ice worms are tough too, surviving the Mount Saint Helens eruption in the firnpack of the newly redeveloping glacier on the mountain.

It is also noteworthy that ice worms only inhabit glaciers. In 2003, we sat at the edge of the Sholes
Glacier looking at the glacier covered Mt. Baker volcano waiting for the sun to
set. After sunset we counted the ice worms on the glacier. There were close to
1000 ice worms per square meter right up to the glacier margin. Because of tremendous
snowfall in 1999 and 2000 a substantial snowpack extended over the ridge at the
edge of the glacier. By the time we had traveled 10 meters from the edge of the
glacier onto this snowpack almost no ice worms existed on the snowpack, within
30 m we could not find a single ice worm. This is true even in cases where the
snowpack adjacent to the glacier survived the summer. Thus, ice worms seem to
require the multi-year glacier ice for survival. In a location such as the Whitechuck Glacier
at right, which is disappearing, the ice worm
population will be lost. The entire rocky area pictured was glaciated 60
years ago.

Where do they occur? Glacier ice worms occur only
in and on glaciers; you won't ever see them more than a few meters from the edge
of a glacier, so they serve as an excellent indicator
of the presence of a glacier ice below the snow. When we performed density
counts extending past the edge of a glacier, out onto a snowfield, ice worm
density dropped dramatically, with no ice worms appearing more than 10 meters
from the edge of the glacier. This suggests that in the course of their
daily vertical migrations they are able to sense when they venture into a
region of thin snowpack, as well that glacier ice is critical for ice worm
survival. What the exact tie is between ice worms and the glacier, we have
yet to find out. Equally important, ice worms cannot
migrate from glacier to glacier, so that populations are isolated from each
other. These populations offer a unique opportunity for testing rates and
mechanisms of evolution.

When to look for ice worms. Ice
worms avoid direct sunlight, so you will be less likely to see them during the
day. They rise to the snow surface on glaciers as the surface becomes
shady in the evening. As shown in the table below, they begin to come out
after 3pm, depending on the shadiness of the location and the time of
year. (The fact that there are no ice worms recorded after 8pm (2000 hrs)
and before 7 am is because we weren't looking then.) Look for ice worms first in the shade created by suncups; later in the evening you will see them virtually cover the surface of glaciers in the
North Cascades; they are more dispersed on Alaskan glaciers. Ice
worms often occur at densities of 2000 or more per square meter on North
Cascades glaciers! They are reported on Alaskan glaciers to occur at
densities of 100 to 200 per square meter.

What do ice worms eat? They do
eat snow algae, which is available in great quantity in the snow, not limited to
the stuff we see as 'watermelon snow' (Goodman 1971). Ice worms graze on
algae in the snow, as well as bacteria and anything else that is small enough to
fit in their mouths (which are tiny indeed). When Goodman dissected ice
worms from Alaska, he found symbiotic single-celled creatures residing there;
these warrant further investigation. Because there is so much algae and so
many ice worms, their role in downstream ecology is probably significant,
both in terms of biomass, and in terms of carbon and other nutrient
processing. The microbial glacier
community that the ice worm relies upon is dominated by unicellular algal
species, with some bacteria, fungi, and multi-celled algae. Observed microbial
densities average about
1.5 organisms/ul. For a glacier with an area of one square kilometer, average
summer runoff is 0.3 cubic meters/second which is 300 liters. Thus, a North Cascade glacier of this size would contribute For a glacier with an outflow of 28 cubic meter/second, a
glacier can contribute over 500 milllion organisms/second downstream in the
summer!

What are ice worm habitats? In
the evening and night hours ice worms feed primarily on the surface of snow on
glaciers, and to a much less degree, on bare ice. During the day, ice
worms hide out beneath the surface of the glacier, avoiding the extreme sunlight
of midday. Ice worms have been reported from several centimeters to
several meters below the surface of snow on glaciers; they have also been
reported as showing up on walls of ice caves tens of meters below the
surface. Please let us know how deep you find ice worms! Ice
Worms have anti-freeze proteins (AFP) which help keep them from freezing solid.
These AFP's inhibit the growth of ice by lowering the freezing point and coating
ice molecules. This facet is seen in other organisms that inhabit
cold environments.

Ice worms are often sighted in the glacier meltwater
pools, slush, and streams found in or on top of glacier ice, even during the
day. It is believed that the water filters the longwave radiation
sufficiently for the ice worms to hang out there during bright periods.
Ice worms feed in pools and streams, keeping one end hooked in the ice while the
other end (apparently the mouth) waves back and forth in the water. They
are very successful hanging on even in very fast and turbulent water, but appear
feed more often in slow to moderately flowing streams on glaciers.

In still pools,
ice worms can be found at extremely high densities either relaxing in muddy
sediment on the bottom, or wrapped together in tight, twisting bundles of
several to 100+ worms. This bundling activity is probably part of
their reproductive cycle, as has been reported for other oligochates. The pool shown
in the photo had more than a
dozen such writhing bundles on the muddy bottom.

Ice Worm Physiology and Morphology

In 2001-2002 field specimens were
collected for lab work at Clark University.Ice worms have curiously few features which appear adapted to their
icy habitat. They have the same basic physical structures as earthworms,
with few obvious morphological changes. They are similarly segmented, have
bundles of setae (hairs) along the bottom for moving, and a mouth pore at one end
. As members of the order Enchytraidae, they also have
very distinctive penial lobes, which don't really remind most of us of
male genital organs. Perhaps most striking is their dark color, with more melanocytes by far than any other worm; this is obviously an adaptation to
protect them from intense UV exposure. Of course, this begs the question as to
why, if they have so much pigment to protect them, must they avoid direct
sunlight so completely. They also utilize anti-freeze proteins
to resist freezing. Dan Shain at Rutgers has examined
the metabolism of ice worms. The key finding of particular interest is
that adenosine triphosphate (ATP), the energy
source for biology, is used differently. In all organisms where
this has been examined from algae, bacteria and humans as temperature drops the
use of ATP and the cellular level of ATP drops. For ice worms it is just
the opposite as temperature drops at least down to 21 F the cellular levels of
ATP rise. This indicates in one respect a metabolism increases, which may
help explain how they do not freeze, but not how this characteristic developed.
We have collected ice worms in recent years for two programs that have
investigated their Anti-freeze Protein capacity.

In a recent paper examining ice worms genetic material in part collected by NCGCP
and from other regions in the Pacific Northwest revealed the presence of two
geographically distinct clades (groups) of ice worms (northern and southern). The northern clade
comprises all Alaskan populations, while the southern clade contains British
Columbia, Washington State, and Oregon State populations. No evidence of gene
flow was detected between these two lineages or between noncontiguous glaciers
throughout their geographic range.

Ice worms die at temperatures much more than 10o
C, and begin to decompose at temperatures above 20o C. Goodman
(1971) suggested that this in part may be due to their acclimation to lower
temperatures, and not inherited physiology alone. Very little else
is known about ice worm physiology and morphology, so we look forward to
learning more about how these critters have adapted to such an extreme
environment.

The variation in density from glacier to glacier is shown
in the table
below. This mean density includes data from all times of the day,
including midday when ice worms are nowhere to be seen; they are therefore much
lower than the actual density of ice worms. These numbers do provide relative densities. Ptarmigan
Ridge's number is elevated relative to the others because its count did not include any
midday
hours. Note that the 'off-glacier' counts are 0. The dramatic
differences between the ice worm heavy glaciers (e.g., Easton, Honeycomb,
Sholes, Suiattle), and those glaciers with a relative disparity of ice worms
(e.g. Columbia, Daniels, Lower Curtis) needs to be further
investigated. Densities in
Alaska tend to be much lower than in the North Cascades.

The recent rapid retreat of North Cascade
glaciers, a loss of 20-40% of their entire volume since 1984 and the
disappearance of 8% of the glaciers we monitor is of great concern. It is
certainly altering the alpine habitat. Use
the links above to further explore these issues. If you have a specific question
you believe is worth our investigating this year.